This invention relates to multi-speed planetary transmissions having three planetary gearsets and five torque-transmitting mechanisms that are selectively engageable in combinations of three to provide at least six forward speeds and one reverse speed.
Passenger vehicles include a powertrain that is comprised of an engine, multi-speed transmission, and a differential or final drive mechanism. The multi-speed transmission increases the overall operating range of the vehicle by permitting the engine to operate through its torque range a number of times as the transmission ratios are interchanged. The number of forward speed ratios that are available in a transmission determines the number of ratio interchanges that can occur and therefore the number of times the engine torque range can be repeated.
Early automatic transmissions had two speed ranges. This severely limited the overall speed range of the vehicle and therefore required a relatively large engine that could produce a wide speed and torque range. This resulted in the engine operating at a specific fuel consumption point, during cruising, other than the most efficient point. Therefore, manually shifted (countershaft transmissions) were the most popular.
With the advent of three and four speed automatic transmissions, the automatic shifting (planetary gear) transmission increased in popularity with the motoring public. These transmissions improve the operating performance and fuel economy of the vehicle. The increased number of speed ratios reduces the step size between ratios and therefore improves the shift quality of the transmission by making the ratio interchanges substantially imperceptible to the operator under normal vehicle acceleration.
It has been suggested that the number of forward speed ratios be increased to five and even six speeds. This has been accomplished in many heavy truck powertrains. Six speed transmissions are disclosed in U.S. Pat. No. 4,070,927 issued to Polak on Jan. 31, 1978; U.S. Pat. No. 6,071,208 issued to Koivunen on Jun. 6, 2000; U.S. Pat. No. 5,106,352 issued to Lepelletier on Apr. 21, 1992; U.S. Pat. No. 5,599,251 issued to Beim and McCarrick on Feb. 4, 1997, U.S. Pat. No. 6,083,135 issued to Baldwin et al. on Jul. 4, 2000, and European Patent Application No. EP 1 033 510 A1 published Jun. 9, 2000.
Six speed transmissions offer several advantages over four and five speed transmissions, including improved vehicle acceleration and improved fuel economy. While many trucks employ six-speed transmissions, such as Polak, passenger cars are still manufactured, for the main part, with three and four speed automatic transmissions, and relatively few five or six speed devices due to the size and complexity of these transmissions. The Polak transmission provides six forward speed ratios with three planetary gearsets, two clutches, and three brakes. The Koivunen and Beim patents utilize six torque transmitting devices including four brakes and two clutches to establish the six forward speed ratios and one reverse ratio. The Lepelletier and the EP publications each employ three planetary gearsets, three clutches and two brakes to provide six forward speed ratios and one reverse ratio. One of the planetary gearsets in each of these publications is positioned and operated to establish two fixed speed input members for the remaining two planetary gearsets.
It is an object of the present invention to provide an improved multi-speed planetary transmission having three planetary gearsets and five torque-transmitting mechanisms.
In one aspect of the present invention, each of the family members has three planetary gearsets and each planetary gearset has three members.
In another aspect of the present invention, the three planetary gear members are either a sun gear member, a ring gear member, or a planet carrier assembly member.
In yet another aspect of the present invention, the five torque-transmitting mechanisms are composed of three rotating type torque-transmitting mechanisms and two stationary type torque-transmitting
In still another aspect of the present invention, each of the family members has three interconnecting members that are effective to continuously interconnect members of the planetary gearsets.
In yet still another aspect of the present invention, a first of the interconnecting members connects a first member of the first planetary gearset with a first member of the second planetary gearset, a second of the fixed interconnecting members continuously interconnects a second member of the second planetary gearset with a first member of the third planetary gearset, and a third of the interconnecting members continuously interconnects a second member of the first planetary gearset with a second member of the third planetary gearset.
In a further aspect of the present invention, an output shaft is continuously connected with at least one member of one of the planetary gearsets.
In yet a further aspect of the present invention, an input shaft for each transmission family member is selectively connectible with the planetary gearsets through a first and second of the rotating torque-transmitting mechanisms.
In yet still a further aspect of the present invention, a third of the rotating torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with one of the input shaft, the output shaft, or another member of one of the planetary gearsets.
In yet a still further aspect of the present invention, the torque-transmitting mechanisms are selectively engaged in combinations of three to provide at least six forward speed ratios and one reverse speed ratio between the input shaft and the output shaft.
Each of the family members, as set forth above in the aspects and object of this invention, have interconnected members and at least one member continuously connected with the output shaft. In each of the family members, at least one of the planetary members of two of the planetary gearsets is non-continuously connected with any other planetary member within the gearsets except for meshing relationships, which are required. In many of the family members, the input shaft is selectively engaged with one of the non-continuously interconnected members through one of the selectively engageable torque-transmitting mechanisms and is selectively engaged with one of the interconnecting members through another of the selectively engageable torque-transmitting mechanisms. In other of the family members, the input shaft is selectively connected to the non-continuously connected members through the two torque-transmitting mechanisms.